I agree with Laurent - ufw already supports gre, gufw just needs to bubble that up.
** Package changed: ufw (Ubuntu) => gui-ufw -- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to ufw in Ubuntu. https://bugs.launchpad.net/bugs/1784937 Title: Add GRE protocol Status in Gufw: New Bug description: Enabling firewall will prevent connecting to remote PPTP server. We need a way to enable the GRE protocol using GUFW. Only TCP and UDP are available to selection for now, even in the advanced screen. To manage notifications about this bug go to: https://bugs.launchpad.net/gui-ufw/+bug/1784937/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : [email protected] Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp

